Congenital myasthenic syndromes by Epsilon subunit mutations: Phenotypic profiles of 17 Algerian families.

BACKGROUND: Congenital myasthenic syndromes (CMS) are a heterogeneous group of rare genetic disorders. The acetyl choline receptor contains five subunits, with a predominance of mutations affecting the epsilon subunit gene called cholinergic receptor nicotinic epsilon (CHRNE) gene. OBJECTIVE: To study the clinical phenotype of 17 families with CHRNE gene mutations. METHODS: We report a series of 17 families with 22 affected patients carrying different mutations encoding CHRNE proteins. RESULTS: We studied their clinical and biological phenotypes, as well as their evolutionary profile and their response to the different therapies proposed. A phenotypic comparison was made between the families carrying the founding Maghrebian mutation and the other mutations found in this series. CONCLUSION: The CHRNE gene mutations are the most frequent ones in CMS. The phenotypes reported in this study are heterogeneous, and can depend on the causative mutation.

Congenital myasthenic syndrome by mutation of the ColQ gene: Phenotypic and evolutionary profile of three Algerian families.

BACKGROUND: Congenital myasthenic syndromes (CMS) are rare genetic neuromuscular disorders. The COLQ gene encoding the collagenous subunit of the acetyl cholinesterase enzyme tail is implicated in a synaptic form of CMS (also called type 5, according to the new gene table 2020 classification). OBJECTIVE: To study the clinical phenotype of three families with COLQ gene mutations. METHODS: We report a series of three consanguineous families, with seven affected patients, carrying three different mutations of the COLQ gene, one of which has never been reported in the literature before. RESULTS: We studied their clinical and paraclinical phenotypes, and try to compare the three families as well as compare them with other series carrying COLQ gene mutations reported in the literature. CONCLUSION: COLQ gene mutations have phenotypic particularities that must be recognized to propose appropriate genetic study.

Dystrophic Myopathy of the Diaphragm with Recurrent Severe Respiratory Failure is Congenital Myasthenic Syndrome 11.

We here present the case of a patient with a congenital myasthenic syndrome (CMS) due to pathogenic variants in the RAPSN gene. During childhood he experienced recurrent episodes of respiratory failure during respiratory infections. This and other cases were reported as isolated dystrophy of the diaphragmatic musculature. In adulthood, whole exome sequencing revealed two heterozygous pathogenic variants in the RAPSN gene. This led to the revision of the diagnosis to rapsyn CMS11 (OMIM:616326, MONDO:0014588). EMG, muscle ultrasound and the revision of muscle biopsies taken in childhood support this diagnosis. After the revision of the diagnosis, treatment with pyridostigmine was started. This resulted in a reduction of fatigability and an improvement in functional abilities and quality of life.

Highly asymmetrical distribution of muscle wasting correlates to the heteroplasmy in a patient carrying a large-scale mitochondrial DNA deletion: a novel pathophysiological mechanism for explaining asymmetry in mitochondrial myopathies.

Mitochondrial diseases are a heterogeneous group of pathologies, caused by missense mutations, sporadic large-scale deletions of mitochondrial DNA (mtDNA) or mutations of nuclear maintenance genes. We report the case of a patient in whom extended muscle pathology, biochemical and genetic mtDNA analyses have proven to be essential to elucidate a unique asymmetrical myopathic presentation. From the age of 34 years on, the patient has presented with oculomotor disorders, right facial peripheral palsy and predominantly left upper limb muscle weakness and atrophy. By contrast, he displayed no motor weakness on the right hemi-body, and no sensory symptoms, cerebellar syndrome, hypoacusis, or parkinsonism. Cardiac function was normal. CK levels were elevated (671 UI/L). Electroneuromyography (ENMG) and muscle MRI showed diffuse myogenic alterations, more pronounced on the left side muscles. Biopsy of the left deltoid muscle showed multiple mitochondrial defects, whereas in the right deltoid, mitochondrial defects were much less marked. Extended mitochondrial biochemical and molecular workup revealed a unique mtDNA deletion, with a 63.4% heteroplasmy load in the left deltoid, versus 8.1% in the right one. This case demonstrates that, in mitochondrial myopathies, heteroplasmy levels may drastically vary for the same type of muscle, rising the hypothesis of a new pathophysiological mechanism explaining asymmetry in hereditary myopathies.

Dunnigan lipodystrophy syndrome: French National Diagnosis and Care Protocol (PNDS; Protocole National de Diagnostic et de Soins).

Dunnigan syndrome, or Familial Partial Lipodystrophy type 2 (FPLD2; ORPHA 2348), is a rare autosomal dominant disorder due to pathogenic variants of the LMNA gene. The objective of the French National Diagnosis and Care Protocol (PNDS; Protocole National de Diagnostic et de Soins), is to provide health professionals with a guide to optimal management and care of patients with FPLD2, based on a critical literature review and multidisciplinary expert consensus. The PNDS, written by members of the French National Reference Center for Rare Diseases of Insulin Secretion and Insulin Sensitivity (PRISIS), is available on the French Health Authority website (in French). Dunnigan syndrome is characterized by a partial atrophy of the subcutaneous adipose tissue and by an insulin resistance syndrome, associated with a risk of metabolic, cardiovascular and muscular complications. Its prevalence, assessed at 1/100.000 in Europe, is probably considerably underestimated. Thorough clinical examination is key to diagnosis. Biochemical testing frequently shows hyperinsulinemia, abnormal glucose tolerance and hypertriglyceridemia. Elevated hepatic transaminases (hepatic steatosis) and creatine phosphokinase, and hyperandrogenism in women, are common. Molecular analysis of the LMNA gene confirms diagnosis and allows for family investigations. Regular screening and multidisciplinary monitoring of the associated complications are necessary. Diabetes frequently develops from puberty onwards. Hypertriglyceridemia may lead to acute pancreatitis. Early atherosclerosis and cardiomyopathy should be monitored. In women, polycystic ovary syndrome is common. Overall, the management of patients with Dunnigan syndrome requires the collaboration of several health care providers. The attending physician, in conjunction with the national care network, will ensure that the patient receives optimal care through regular follow-up and screening. The various elements of this PNDS are described to provide such a support.

Home-based exercise in autoimmune myasthenia gravis: A randomized controlled trial.

The tolerance of exercise and its effects on quality of life in myasthenia gravis are not currently backed up by strong evidence. The aim of this study was to determine whether exercise as an adjunct therapy is well tolerated and can improve health-related quality of life (HRQoL) in stabilized, generalized autoimmune myasthenia gravis (gMG). We conducted a parallel-group, multi-center prospective RCT using computer-generated block randomization. Adults with stabilized, gMG, and no contra-indication to exercise, were eligible. Participants received usual care alone or usual care and exercise. The exercise intervention consisted of 3-weekly 40 min sessions of an unsupervised, moderate-intensity home rowing program over 3 months. The primary endpoint was the change in HRQoL from randomization to post-intervention. Assessor-blinded secondary endpoints were exercise tolerance and effects on clinical, psychological and immunological status. Of 138 patients screened between October 2014 and July 2017, 45 were randomly assigned to exercise (n = 23) or usual care (n = 20). Although exercise was well tolerated, the intention-to-treat analysis revealed no evidence of improved HRQoL compared to usual care (MGQOL-15-F; mean adjusted between-groups difference of -0.8 points, 95%CI -5.4 to 3.7). Two patients hospitalized for MG exacerbation were from the usual care group.

Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies.

BACKGROUND AND PURPOSE: To describe a large series of patients with α, ß, and γ sarcoglycanopathies (LGMD-R3, R4, and R5) and study phenotypic correlations and disease progression. METHODS: A multicentric retrospective study in four centers in the Paris area collecting neuromuscular, respiratory, cardiac, histologic, and genetic data. The primary outcome of progression was age of loss of ambulation (LoA); disease severity was established according to LoA before or after 18 years of age. Time-to-event analysis was performed. RESULTS: One hundred patients (54 γ-SG; 41 α-SG; 5 ß-SG) from 80 families were included. The γ-SG patients had earlier disease onset than α-SG patients (5.5 vs. 8 years; p = 0.022) and ß-SG patients (24.4 years). Axial muscle weakness and joint contractures were frequent and exercise intolerance was observed. At mean follow-up of 22.9 years, 65.3% of patients were wheelchair-bound (66.7% α-SG, 67.3% γ-SG, 40% ß-SG). Dilated cardiomyopathy occurred in all sarcoglycanopathy subtypes, especially in γ-SG patients (p = 0.01). Thirty patients were ventilated and six died. Absent sarcoglycan protein expression on muscle biopsy and younger age at onset were associated with earlier time to LoA (p = 0.021 and p = 0.002). Age at onset was an independent predictor of both severity and time to LoA (p = 0.0004 and p = 0.009). The α-SG patients showed genetic heterogeneity, whereas >90% of γ-SG patients carried the homozygous c.525delT frameshift variant. Five new mutations were identified. CONCLUSIONS: This large multicentric series delineates the clinical spectrum of patients with sarcoglycanopathies. Age at disease onset is an independent predictor of severity of disease and LoA, and should be taken into account in future clinical trials.

Scapular dyskinesis in myotonic dystrophy type 1: clinical characteristics and genetic investigations.

OBJECTIVE: To study scapular winging or other forms of scapular dyskinesis (condition of alteration of the normal position and motion of the scapula) in myotonic dystrophy type 1 (DM1), which is generally considered to be a distal myopathy, we performed an observational cohort study. METHODS: We performed a prospective cohort study on the clinical features and progression over time of 33 patients with DM1 and pronounced, mostly asymmetric scapular winging or other forms of scapular dyskinesis. We also explored if scapular dyskinesis in DM1 has the same genetic background as in facioscapulohumeral muscular dystrophy type 1 (FSHD1). RESULTS: The cohort included patients with congenital (n = 3), infantile (n = 6) and adult-onset DM1 (n = 24). Scapular girdle examination showed moderate shoulder girdle weakness (mean MRC 3) and atrophy of trapezius, infraspinatus, and rhomboid major, seemingly similar as in FSHD1. Shoulder abduction and forward flexion were limited (50-70°). In five patients, scapular dyskinesis was the initial disease symptom; in the others it appeared 1-24 years after disease onset. Follow-up data were available in 29 patients (mean 8 years) and showed mild to severe increase of scapular dyskinesis over time. In only three patients, DM1 coexisted with a FSHD mutation. In all other patients, FSHD was genetically excluded. DM2 was genetically excluded in nine patients. The clinical features of the patients with both DM1 and FSHD1 mutations were similar to those with DM1 only. CONCLUSION: Scapular dyskinesis can be considered to be part of DM1 in a small proportion of patients. In spite of the clinical overlap, FSHD can explain scapular dyskinesis only in a small minority. This study is expected to improve the recognition of shoulder girdle involvement in DM1, which will contribute to the management of these patients.

Life-threatening lactic acidosis occurring in adults with mitochondrial disorders.

Although relatively common in children, severe acute lactic acidosis is rare in adults with mitochondrial myopathies. We report here three cases, aged 27, 32 and 32 years, who developed life-threatening metabolic crisis with severe lactic acidosis, requiring hospitalisation in intensive care unit. Plasma lactates were elevated 10 to 15 fold normal values, necessitating extra-renal dialysis. By contrast CK levels were moderately increased (3 to 5N). No triggering factor was identified, but retrospectively all patients reported long-lasting mild muscle fatigability and weakness before their acute metabolic crisis. All of them recovered after prolonged intensive care but resting lactate levels remained elevated. Muscle biopsy showed ragged-red and COX-negative fibers in two patients and mild lipidosis in the third one. Heteroplasmic pathogenic point mutations were detected in MT-TL1 (m.3280G>A;m.3258C>T) and MT-TK (m.8363A>G). Life-threatening lactic acidosis may thus be a major inaugural clinical manifestation in adults with mitochondrial myopathies. Prolonged intensive care may lead to a dramatic and sustained improvement and is mandatory in such cases.

Childhood-onset form of myotonic dystrophy type 1 and autism spectrum disorder: Is there comorbidity?

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder with neuromuscular symptoms and brain dysfunctions. Depending on the phenotypic expression, the degree of cognitive impairment remains heterogeneous, ranging from moderate to severe intellectual disability in the congenital form, to executive, visuospatial and personality dysfunction in the adult-onset form. Studies exploring the cognitive or psychiatric impairments in the childhood form of DM1, characterized by an age of onset between one and ten years, uneventful pre and post natal history and normal development the first year of life, are scarce and show conflicting results in regard to a comorbid diagnosis of Autism Spectrum Disorder (ASD). The aim of the current review is to summarize diagnostic criteria and update the state of the debate regarding comorbidity. Evidence from 9 studies collected in PubMed database (representing a total of 175 cases) focusing on clinical, neuropsychological and neuroimaging domains in childhood DM1 is considered and similarities or differences between childhood DM1 and ASD are identified. Highlighting what is known about the neurocognitive features specific to the childhood-onset form of DM1 could help (1) propose early screening regarding socio-emotional and attentional/executive functions or (2) implement therapeutic programs based on reinforcement of executive skills or social cognition.

Diagnostic anoctamin-5 protein defect in patients with ANO5-mutated muscular dystrophy.

AIMS: Previously, detection of ANO5 protein has been complicated by unspecific antibodies, most of which have not identified the correct protein. The aims of the study were to specify ANO5 protein expression in human skeletal muscle, and to investigate if the ANO5 protein levels are affected by different ANO5 mutations in anoctaminopathy patients. METHODS: Four different antibodies were tested for ANO5 specificity. A sample preparation method compatible with membrane proteins, combined with tissue fractionation was used to determine ANO5 expression in cell cultures expressing ANO5, in normal muscles and eight patient biopsies with six different ANO5 mutations in homozygous or compound heterozygous states, and in other dystrophies. RESULTS: Only one specific monoclonal N-terminal ANO5 antibody was efficient in detecting the protein, showing that ANO5 is expressed as a single 107 kD polypeptide in human skeletal muscle. The truncating mutations c.191dupA and c.1261C>T were found to abolish ANO5 expression, whereas the studied point mutations had variable effects; however, all the ANO5 mutations resulted in clearly reduced ANO5 expression in the patient muscle membrane fraction. Attempts to detect ANO5 using immunohistochemistry were not yet successful. CONCLUSIONS: The data presented here indicate that the ANO5 protein expression is decreased in ANO5-mutated muscular dystrophy and that most of the non-truncating pathogenic ANO5 mutations likely destabilize the protein and cause its degradation. The method described here allows direct analysis of human ANO5 protein, which can be used in diagnostics, for evaluating the pathogenicity of the potentially harmful ANO5 variants of uncertain significance.

Prediction of long-term prognosis by heteroplasmy levels of the m.3243A>G mutation in patients with the mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome.

BACKGROUND AND PURPOSE: Our aim was to determine the prognostic value of urine and blood heteroplasmy in patients with the m.3243A>G mutation. METHODS: Adults with the m.3243A>G mutation referred to our institution between January 2000 and May 2014 were retrospectively included. The relationship between their baseline clinical characteristics, their mutation load in urine and blood, and major adverse events (MAEs) during follow-up, defined as medical complications requiring a hospitalization or complicated by death, was studied. RESULTS: Of the 43 patients (age 45.6 ± 13.3 years) included in the study, 36 patients were symptomatic, including nine with evidence of focal brain involvement, and seven were asymptomatic. Over a 5.5 ± 4.0 year mean follow-up duration, 14 patients (33%) developed MAEs. Patients with MAEs had a higher mutation load than others in urine (60.1% ± 13.8% vs. 40.6% ± 26.2%, P = 0.01) and in blood (26.9% ± 18.4% vs. 16.0% ± 12.1%, P = 0.03). Optimal cutoff values for the prediction of MAEs were 45% for urine and 35% for blood. In multivariate analysis, mutation load in urine ≥45% [odds ratio 25.3; 95% confidence interval (CI) 1.1-567.8; P = 0.04], left ventricular hypertrophy (odds ratio 16.7; 95% CI 1.3- 222.5; P = 0.03) and seizures (odds ratio 48.3; 95% CI 2.5-933; P = 0.01) were associated with MAEs. CONCLUSIONS: Patients with the m.3243A>G mutation are at high risk of MAEs, which can be independently predicted by mutation load in urine ≥45%, a personal history of seizures, and left ventricular hypertrophy.

Unravelling the myotonic dystrophy type 1 clinical spectrum: A systematic registry-based study with implications for disease classification.

The broad clinical spectrum of myotonic dystrophy type 1 (DM1) creates particular challenges for both medical care and design of clinical trials. Clinical onset spans a continuum from birth to late adulthood, with symptoms that are highly variable in both severity and nature of the affected organ systems. In the literature, this complex phenotype is divided into three grades (mild, classic, and severe) and four or five main clinical categories (congenital, infantile/juvenile, adult-onset and late-onset forms), according to symptom severity and age of onset, respectively. However, these classifications are still under discussion with no consensus thus far. While some specific clinical features have been primarily reported in some forms of the disease, there are no clear distinctions. As a consequence, no modifications in the management of healthcare or the design of clinical studies have been proposed based on the clinical form of DM1. The present study has used the DM-Scope registry to assess, in a large cohort of DM1 patients, the robustness of a classification divided into five clinical forms. Our main aim was to describe the disease spectrum and investigate features of each clinical form. The five subtypes were compared by distribution of CTG expansion size, and the occurrence and onset of the main symptoms of DM1. Analyses validated the relevance of a five-grade model for DM1 classification. Patients were classified as: congenital (n=93, 4.5%); infantile (n=303, 14.8%); juvenile (n=628, 30.7%); adult (n=694, 34.0%); and late-onset (n=326, 15.9%). Our data show that the assumption of a continuum from congenital to the late-onset form is valid, and also highlights disease features specific to individual clinical forms of DM1 in terms of symptom occurrence and chronology throughout the disease course. These results support the use of the five-grade model for disease classification, and the distinct clinical profiles suggest that age of onset and clinical form may be key criteria in the design of clinical trials when considering DM1 health management and research.

Multiple acyl-CoA dehydrogenase deficiency (MADD) as a cause of late-onset treatable metabolic disease.

INTRODUCTION: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare, treatable, beta-oxidation disorder responsible for neuromuscular symptoms in adults. This case series describes the clinical and biochemical features of 13 French patients with late-onset MADD. METHODS AND RESULTS: Thirteen ambulant patients (eight women, five men), with a median age at onset of 27 years, initially experienced exercise intolerance (n=9), isolated muscle weakness (n=1) and a multisystemic pattern with either central nervous system or hepatic dysfunction (n=3). During the worsening period, moderate rhabdomyolysis (n=5), a pseudomyasthenic pattern (n=5) and acute respiratory failure (n=1) have been observed. Weakness typically affected the proximal limbs and axial muscles, and there was sometimes facial asymmetry (n=3). Moderate respiratory insufficiency was noted in one case. Median baseline creatine kinase was 190IU/L. Lactacidemia was sometimes moderately increased at rest (3/10) and after exercise (1/3). The acylcarnitine profile was characteristic, with increases in all chain-length acylcarnitine species. Electromyography revealed a myogenic pattern, while muscle biopsy showed lipidosis, sometimes with COX-negative fibers (n=2). The mitochondrial respiratory chain was impaired in five cases, with coenzyme Q10 decreased in two cases. All patients harbored mutations in the ETFDH gene (four homozygous, seven compound heterozygous, two single heterozygous), with nine previously unidentified mutations. All patients were good responders to medical treatment, but exercise intolerance and/or muscular weakness persisted in 11 of them. CONCLUSION: Late-onset forms of MADD may present as atypical beta-oxidation disorders. Acylcarnitine profiling and muscle biopsy remain the most decisive investigations for assessing the diagnosis. These tests should thus probably be performed more widely, particularly in unexplained cases of neuromuscular and multisystemic disorders.

Myofibrillar myopathies: State of the art, present and future challenges.

Myofibrillar myopathies (MFM) have been described in the mid-1990s as a group of diseases sharing common histological features, including an abnormal accumulation of intrasarcoplasmic proteins, the presence of vacuoles and a disorganization of the intermyofibrillar network beginning at the Z-disk. The boundaries of this concept are still uncertain, and whereas six genes (DES, CRYAB, LDB3/ZASP, MYOT, FLNC and BAG3) are now classically considered as responsible for MFM, other entities such as FHL1 myopathy or Hereditary Myopathy with Early Respiratory Failure linked to mutations of titin can now as well be included in this group. The diagnosis of MFM is not always easy; as histological lesions can be focal, and muscle biopsy may be disappointing; this has led to a growing importance of muscle imaging, and the selectivity of muscle involvement has now been described in several disorders. Due to the rarity of these myopathies, if some clinical patterns (such as distal myopathy associated with cardiomyopathy due to desmin mutations) are now well known, surprises remain possible and should lead to systematic testing of the known genes in case of a typical histological presentation. In this paper, we aim at reviewing the data acquired on the six main genes listed above as well as presenting the experience from two French reference centres, Paris and Marseilles.

[Congenital myasthenic syndromes in childhood: Drug therapeutic strategies]. / Syndromes myasthéniques congénitaux de l'enfant : stratégies thérapeutiques médicamenteuses.

Congenital myasthenia syndromes (CMS) are a group of genetic disorders responsible for neuromuscular junction dysfunction. Usually beginning before 2 years of age, they are revealed by fatigability and muscle weakness, especially after stress, and often prevent the child's normal development. Over recent years, major advances in therapeutic strategies have been made following the discovery of numerous mutations responsible for CMS and the understanding of their pathogenic role. Here we report a pediatric CMS case caused by a mutation of the ɛ subunit of the acetylcholine receptor. The initial treatment with acetylcholinesterase inhibitor rapidly showed its limits in terms of both effectiveness and tolerance. The association with 3.4 diaminopyridine (DAP), a new drug available to treat such conditions, has transformed the motor outcome of our patient and allowed psychomotor development. In addition to 3.4 DAP, other molecules adapted to other types of CMS are now available. Three major groups of CMS can be distinguished depending on whether the deficit is at the presynaptic, synaptic, or postsynaptic level of the neuromuscular junction. Depending on the type of CMS, therapeutic management may include acetylcholinesterase inhibitors, 3.4 DAP, fluoxetine, quinidine sulfate, or ephedrine. With the case report, we provide a recent review of the literature on such new therapeutic options, their indications and restrictions, their mechanism of action, and prescription modalities. Knowing the precise CMS type and the appropriate therapeutic options available is essential for the proper management of such chronic and severe but relatively treatable childhood disorders.

Diagnostic power of the non-ischaemic forearm exercise test in detecting glycogenosis type V.

BACKGROUND AND PURPOSE: This was a retrospective study to assess the diagnostic value of the non-ischaemic forearm exercise test in detecting McArdle's disease. METHODS: The study is a retrospective diagnostic study over 15 years (1999-2013) on a referred sample of patients suffering from exercise intolerance and various muscle complaints, generally with elevated creatine kinase (CK). In all, 1226 patients underwent the non-ischaemic forearm exercise test. Blood lactate, ammonia and CK levels were analyzed. DNA analyses and/or muscle biopsies were assessed to confirm the diagnosis of McArdle's disease. The results of 60 volunteers were used to compare with the results of study subjects. RESULTS: In this cohort, 40 patients were finally diagnosed with McArdle's disease. Absolute values of lactate and ammonia rise were used to discriminate all McArdle patients from healthy patients. A sensitivity and specificity of respectively 100% and 99.7% were calculated. The 24-h CK level showed no significant difference from the CK level at the day of the test and confirms the safety of the test. CONCLUSIONS: This study has formally assessed the diagnostic value of the non-ischaemic forearm exercise test in the detection of McArdle's disease. Very high sensitivity and specificity were observed. Furthermore, the test is easy to set up and to perform, it is non-traumatic and cost effective. It may circumvent a muscle biopsy in McArdle patients presenting the most common mutations. Hence, it is a perfect and safe screening instrument to detect patients with McArdle's disease. Glycogen storage disease type III patients, however, may show similar patterns to McArdle patients.

Bethlem myopathy: long-term follow-up identifies COL6 mutations predicting severe clinical evolution.

OBJECTIVE: Mutations in one of the 3 genes encoding collagen VI (COLVI) are responsible for a group of heterogeneous phenotypes of which Bethlem myopathy (BM) represents the milder end of the spectrum. Genotype-phenotype correlations and long-term follow-up description in BM remain scarce. METHODS: We retrospectively evaluated the long-term clinical evolution, and genotype-phenotype correlations in 35 genetically identified BM patients (23 index cases). RESULTS: Nineteen patients showed a typical clinical picture with contractures, proximal weakness and slow disease progression while 11 presented a more severe evolution. Five patients showed an atypical presentation, namely a limb girdle muscle weakness in 2 and a congenital myopathy pattern with either no contractures, or only limited to ankles, in 3 of them. Pathogenic COL6A1-3 mutations were mostly missense or in frame exon-skipping resulting in substitutions or deletions. Twenty one different mutations were identified including 12 novel ones. The mode of inheritance was, autosomal dominant in 83% of the index patients (including 17% (N=4) with a de novo mutation), recessive in 13%, and undetermined in one patient. Skipping of exon 14 of COL6A1 was found in 35% of index cases and was mostly associated with a severe clinical evolution. Missense mutations were detected in 39% of index cases and associated with milder forms of the disease. CONCLUSIONS: Long-term follow-up identified important phenotypic variability in this cohort of 35 BM patients. However, worsening of the functional disability appeared typically after the age of 40 in 47% of our patients, and was frequently associated with COL6A1 exon 14 skipping.

Antibodies to clustered acetylcholine receptor: expanding the phenotype.

BACKGROUND AND PURPOSE: To provide a detailed phenotypical description of seronegative patients with generalized myasthenia gravis and antibodies to clustered acetylcholine receptors (AChRs) and to assess their frequency amongst a French seronegative generalized myasthenia gravis (SNMG) population. METHODS: A French SNMG database was created and the sera from the 37 patients included in it were analysed by immunofluorescence of cell-based assays using cotransfection of AChR subunit genes together with rapsyn to densely cluster the AChRs. RESULTS: Sixteen per cent (n = 6) of the SNMG patients were found to have antibodies to clustered AChR. They presented either with early onset MG and thymic hyperplasia, late onset MG and thymic involution, or thymoma associated MG. They responded well to cholinesterase inhibitors and immunosuppressants. CONCLUSIONS: Patients with antibodies to clustered AChR account for a significant proportion of SNMG patients and resemble patients with AChR antibodies detected by standard radio-immunoprecipitation.